Abstract: Cardiovascular diseases (CVDs) are a major cause of morbidity and mortality world-wide, and there are significant sex differences in their incidence, pathophysiology, and prognosis. Accumulating evidence suggests an important role for early-life toxicant exposures in the etiology of CVDs; however, the molecular mechanisms underlying these associations are unclear. In particular, the role for sex as a determinant of susceptibility to toxicant-induced cardiovascular health effects remains poorly understood. Pb exposure continues to pose a significant public health concern, particularly in poor urban areas. Perinatal and adult exposure to Pb are associated with adverse cardiovascular effects in human and animal models. One important mechanism by which early Pb exposure may influence the long-term risk of CVDs is through disruption of the precise epigenetic programs governing normal cardiac development. Recent studies in cancer and stem cell biology demonstrate that epigenetic changes and cellular differentiation are closely coupled to the metabolic state of the cell, enabling cells to detect, and rapidly respond to, environmental cues. Notably, stem cells from male and female donors exhibit intrinsic differences in differentiation programs, as well as differential sensitivity to toxicant exposures. Despite known impacts of Pb exposure on heart function, the effects of developmental Pb exposure on epigenetic and metabolic programming during cardiac development, and potential sex differences in these effects, have not been investigated. Using an established mouse model of perinatal environmental exposures, we have recently discovered that developmental Pb exposure leads to sex-specific changes in DNA methylation in the hearts of adult offspring mice. We have further discovered that hearts of Pb-exposed mice exhibit a significant increase in the oxidation of glutathione, a cellular antioxidant and metabolite that is closely coupled to epigenetic programming and stem cell differentiation. These results suggest that perinatal Pb exposure may disrupt normal metabolic and epigenetic programming in the heart in a sex-specific manner. Using human patient-derived induced pluriopotent stem cells (iPSCs) from male and female donors, the goal of this proposal is to elucidate the precise molecular mechanisms underlying Pb-induced programming on human cardiac differentiation and function, and to understand how sex differences may influence susceptibility to this toxicant. Preliminary studies in human iPSC-derived cardiomyocytes demonstrate that acute Pb exposure promotes a dose-dependent increase in action potential duration, suggesting that Pb may have arrhythmogenic effects, and demonstrating the utility of this model to assess Pb-induced effects on cardiac function. The training and research outlined in this K01 proposal will provide an outstanding framework for the development of a successful R01 application and an impactful career as an independent investigator in this understudied area of environmental health.